﻿#ifndef SRC_UTIL_FUNCTION_TRAITS_H_
#define SRC_UTIL_FUNCTION_TRAITS_H_

#include <tuple>

namespace toolkit
{

	template<typename T>
	struct function_traits;

	//普通函数
	template<typename Ret, typename... Args>
	struct function_traits<Ret(Args...)>
	{
	public:
		enum { arity = sizeof...(Args) };
		typedef Ret function_type(Args...);
		typedef Ret return_type;
		using stl_function_type = std::function<function_type>;
		typedef Ret(*pointer)(Args...);

		template<size_t I>
		struct args
		{
			static_assert(I < arity, "index is out of range, index must less than sizeof Args");
			using type = typename std::tuple_element<I, std::tuple<Args...> >::type;
		};
	};

	//函数指针
	template<typename Ret, typename... Args>
	struct function_traits<Ret(*)(Args...)> : function_traits<Ret(Args...)> {};

	//std::function
	template <typename Ret, typename... Args>
	struct function_traits<std::function<Ret(Args...)>> : function_traits<Ret(Args...)> {};

	//member function
#define FUNCTION_TRAITS(...) \
    template <typename ReturnType, typename ClassType, typename... Args>\
    struct function_traits<ReturnType(ClassType::*)(Args...) __VA_ARGS__> : function_traits<ReturnType(Args...)>{}; \

	FUNCTION_TRAITS()
		FUNCTION_TRAITS(const)
		FUNCTION_TRAITS(volatile)
		FUNCTION_TRAITS(const volatile)

		//函数对象
		template<typename Callable>
	struct function_traits : function_traits<decltype(&Callable::operator())> {};

} /* namespace toolkit */

#endif /* SRC_UTIL_FUNCTION_TRAITS_H_ */
